The present invention relates to an experimental technique in microgravity environments, such as space, and more specifically to a crystallization apparatus for crystallizing biological macromolecular substances such as proteins, enzymes etc.
Recently, space environments have been increasingly tried as sites for growing various crystals and production of new materials, such as semiconductors, alloys, biomaterials, etc. Experiments in crystallization of biological substances are one type of experiment increasingly expected to be performed in space. However, biological substances crystallization experiments have such poor repeatability that a plurality of experiments using the same composition and under the same conditions must be conducted.
However, space experiments not only incur costs of transportation to space, but also opportunities to perform them are limited. Furthermore, in experiments in unmanned artificial satellites, the apparatuses must be totally automated. Even in experiments in manned satellites, the time and labor that crews can allot for the experiments are very limited. In view of this, experimental apparatuses which can conduct a plurality of experiments concurrently and that have high reliability are required.
As a conventional biological macromolecular substances crystallization apparatus, an experimental apparatus made by U.S. Payload Systems Inc. (PSI) for growing crystals by vapor diffusion method is known (FIG. 4).
The PSI biological macromolecular substances crystallization apparatus comprises a plate-shaped base 10 of polymethyl pentene, which does not react with water and macromolecular materials, and a block-shaped lid 12. In the base 10 there are provided cylindrical grooves 14, and trench-like grooves 16 around the cylindrical grooves 14. In the lid 12 there are provided screw plugs 18 which shut a biological macromolecular substances solution A off from a crystallizing agent solution B when the experiments are in the stand-by state. Rubber members 20 for tight sealing the cylindrical grooves 14 are provided on one end of the plugs 18. O-rings 22 are provided between the base 10 and the lid 12 and on the plugs 18 respectively for tight sealing the interior of the apparatus with respect to the outside (FIG. 4).
A plurality of such experimental vessels are formed in the base 10 in one-piece therewith. Experiments can be concurrently conducted under different conditions.
In an experiment, a biological macromolecular substances solution A, comprising a protein and neutral salt, is loaded in a cylindrical groove 14 and a crystallizing agent solution B, containing neutral salt of a high concentration and/or organic material is loaded in a trench-like groove 16. In storage, and during standby and launch, the cylindrical groove 14 is tightly sealed at the top by the plug 18 so as to keep the solutions inert and prevent spilling the solutions (FIG. 4, left side). In the experiment, the plug 18 is loosened to allow crystal growth by vapor diffusion (FIG. 4, right side).
An advantage of the PSI apparatus is that the shape of the crystallization vessel is very similar to that of laboratory crystallization vessels used on the earth. Before a space experiment, it is necessary to conduct pre-experiments to determine conditions for the space experiment. However, an advantage of the PSI apparatus is that the shape of the crystallization vessel is similar to those used in laboratories on earth. Because of this similarity of shapes, not so many pre-experiments are necessary. This advantage is not found in other prior art apparatuses.
However, the above-described conventional biological macromolecular substances crystallization apparatus has the problem that because the volume of the interior of the apparatus changes greatly between before and after an experiment, there are risks that the solutions in one experimental vessel may leak into an adjacent one and water may intrude into the experimental vessels from the outside. As a result, the internal pressure of the vessels adversely becomes different from that in an experiment on earth, so that experimental results, such as crystal growth rates, etc., are affected.
A common disadvantage of apparatuses for use in vapor diffusion is that if the vessels are subject to vibrations, specimen solutions are splashed due to gas-liquid interfaces which freely vibrate.
Furthermore, in the above-described biological macromolecular substances crystallization apparatus, although a plurality of experimental vessels are formed in the base in one-piece therewith, the respective vessels are not independent within the tight sealing unit. When specimens of different kinds or specimens of different solution compositions are loaded in the vessels, there is a risk that different specimen solutions may be mixed with one another. In addition, when specimens are loaded into the vessels, or specimens in the vessels are analyzed, inconveniently the common lid is opened, and all the vessels are concurrently exposed.